I was thinking that the ’60 models had the automatic choke hooked to the exhaust manifold but that may not be the case with your particular manifold.  Your exhaust leak may be from the hole in the manifold that the automatic choke tube hooks to.  If that’s the case, then there’s a tube that goes through the manifold to allow air to be heated by the exhaust and that tube has rotted through thus allowing exhaust to escape to the outside of the manifold.  Plugging the hole at both sides will eliminate the exhaust leak.

Lorena, Texas (South of Waco)

On the passenger side of the intake manifold I have an opening that is letting the exhaust gas come through.  Never noticed it until this leak started.  I know that this is the exhaust gas bypass but I have put ram horn headers on my engine and don't have the control valve on the exhaust.  I looked at the shop manual for my '60 F-100 but didn't see it mentioned.  Can I just plug this hole or what should I do with it?  Thanks in advance for any info you can give me.